Expressions, functions, constants, commands, variables, vectors, and control structures may be assembled into scripts within a .control ... .endc section of the input file. The script allows to automate any ngspice task: simulations to perform, output data to analyze, repeat simulations with modified parameters, assemble output plot vectors. The ngspice scripting language is not very powerful, but well integrated into the simulation flow.

The ngspice script input file contains the usual circuit netlist, modelcards, and the actual script, enclosed in a .control .. .endc section. Ngspice is started in interactive mode with the input file on the command line (or sourced later with the source command). After reading the input file the command sequence is immediately processed. Variables or vectors set by previous commands may be referenced by the commands following them. Data can be stored, plotted or grouped into new vectors for either plotting or other means of data evaluation.

The input file may contain only the .control .. .endc section. To notify ngspice about this (not mandatory), the script may start with *ng_script in the first line.